This invention relates to run flat all terrain vehicle tires. As used herein all terrain vehicle tires include tires for such vehicles as small tractors, lawnmowers, ATV, golf carts, skid steer and other light vehicles.
The present invention relates to a run flat tire for all terrain vehicles wherein the tire has a unique tread sidewall structure that permits the tire to be run without being inflated. The inventor of the present invention was also a co-inventor of the unique bead construction for A.T.V. tires which prevented the tire from dislodging from the rim, in the event of a flat. In his earlier patent application, Ser. No. 08/616,360, he provided an interesting background of all terrain vehicle tires. These tires are generally wide and relatively tall in comparison to their nominal rim diameters, which generally range from 8 inches to 12 inches. In that patent application Mr. Rooney had indicated the level of technology as it related to run flat A.T.V. type vehicle tires. And more importantly the general state of the art of run flat tires generally. In developing that tire Mr. Rooney discovered that with all terrain vehicles which carry relatively light loads at low inflation pressures, it was possible to build a tire that could be operated in a totally non-pneumatic fashion. In other words the tire could be designed such that no air pressure was needed above atmospheric conditions.
Having discovered this was a practical solution to A.T.V. tire design, Mr. Rooney has further discovered that enhancements to an all terrain vehicle run flat tire having unlimited run flat capability could be achieved by optimization of both the tread design and the underlying tire structure.
The most relevant prior art document U.S. Pat. No. 4,687,037 is a passenger tire having the features recited in the preamble of claim 1 that portion of the claim after the characterizing clause being novel and inventive over that reference. Each dependent claim defines features of the preferred embodiment tire.
An all terrain vehicle run flat tire (10) is disclosed the tire has an annular tread (12) the tread (12) having a pair of lateral edges (14, 16), the distance half way between the lateral edges (14, 16) defining the equatorial plane of the tire (10). The tread (12) has a plurality of tread lugs (92, 94) in a central rib (95). The plurality of tread lugs (92, 94) are disposed on each tread half and are spaced axially from the equatorial plane, a distance of at least 5% of the tread width. The central rib (95) is located between and separates the plurality of tread lugs (92) on each tread half. The central rib (95) has a height as measured from the inner tread surface of the tire of less than the maximum height of the tread lugs. The tire has a casing radially inward of this tread. In the preferred embodiment, the height of the central rib (95) is less than half the height of the tread lugs. Preferably the central rib (95) has a plurality of narrow grooves or sipes (95) extending across the rib, (95) the narrow grooves being of a depth less that 75% of the height of the central rib.
The tread lugs (92, 94) have a radially outer surface; the radially outer surface defining the net contact area when measured on a flat hard surface. The net contact area is located substantially equally on each tread half and is spaced from the central plane or equatorial plane a distance of at least 5% of the tread width. The tread lugs (92) has a net surface area representing at least 50% of the net contact area of the total tread lugs (92,94). Each tread lug (92) may have at least one narrow groove (91, 93) transversely extending or crossing the enlarged inner portion of the tread lug (92). The narrow groove has a depth of less than 75% of the tread lug height.
The all terrain vehicle run flat tire of the present invention has a casing which has a cord reinforced breaker structure radially inward of the tread, at least one ply reinforcing structure radially inward of the breaker reinforcing structure and extending radially inwardly to a pair of substantially inextensible bead cores, a pair of run flat inserts, one run flat insert being radially inward of the ply reinforcing structure and extending from radially under the breaker structure and one bead core. In the preferred embodiment the casing further has a third run flat insert located between the breaker reinforcing structure and at least one ply reinforcing structure. The third insert (70) extends laterally overlapping the pair of run flat inserts (42). The third insert (70) underlying the tread structure provides improved uninflated handling characteristics greatly stiffening the area between the lateral edges (14,16) of the tread (12) and in combination with the other sidewall inserts (42) provide superb run flat capability.